Bevel protractor



v. H. GREY BEVEL PROTRACTOR Oct. 22, 1946.

Filed Aug. 25, 1944 Patented Oct. 22, 1946 Zttllii omisol .STATES PATENT omer.

BEVEL PROTRACTOR Vernon Henry Grey,v Coventry, England Application August 23, 1944, Serial No. 550,712?` In Great Britain February 27, 1943 3 Claims.` 1

This invention relates to protractors and the like measuring instruments, such as are used by engineers for checking and determining angles, and more particularly to the kind comprising a head having a xed tangential blade, a calibrated dial plate rotatably mounted on said head, and an adjustable blade arranged to slide tangentially of said dial plate and to be rigidly locked thereto.

The object of the present invention is to provide improved means for locking the adjustable blade to the dial plate.

For this purpose according to the present invention there is associated with the dial plate a locking plate and means for moving the same relatively thereto for the purpose of clamping the adjustable blade to the dial plate.

The said locking plate, which turns with the dial plate, is releasably secured thereto at one end by means of a clamping screw and nut and has a, limited amount of radial movement relatively thereto.

The means employed for operating the locking plate consists of a sleeve nut carried by a stud xed in the dial plate and having a coned end adapted to engage and co-operate with a corresponding outwardly coned hole or bush in the locking plate through which the said stud protrudes, the inner and smaller end of said conical hole or bush being of slightly larger diameter than that of the stud. The free or outer end of the locking plate is formed on one side with a transverse rib or projection with which a longitudinal groove in the adjustable blade is adapted for sliding engagement. The arrangement is such that on slackening the clamping nut the locking plate can be moved to clamp the adjustable blade to the dial plate by screwing the conical end of .the sleeve nut into the conical hole or bush in the locking plate, after which the clamping screw and nut can be retightened.

In the accompanying drawing,

Figure 1 is a planview of a protractor embodying the present invention.

Hgure 2 is an edge View thereof.

Figures 3 and 4 are detail sectional views on a larger scale showing the locking plate in its inoperative and operative positions respectively.

Figure 5 is a detail plan View on a scale of the locking plate and associated parts.

Throughout the drawing like parts are designated by similar reference characters.

Referring to the drawing, the invention is shown as applied to an engineers protractor of the kind comprising a circular head a having a fixed tangential blade b, a calibrated dial plate c 2. rotatably mounted on said head, and an adjust-r able blade or straight edge d arranged to slide tangentially of said` dial plate and to be rigidly locked thereto The dial. dat@ is. formed with a a@ Surface C at one part 0f. its. periphery and the means eg;-- ployed according to this invention for locking the adjustable blade d thereto consists of a locking plate e which, together with the dial plate is pivotally secured at one end to a boss a1 on the head a by means of a central stud f and nut h and is provided at the underside of its other end with a transverse rib e1 or projection with which a longitudinal groove d1 in the upper face of the adjustable blade d is in sliding engagement.

The locking of the blade d to the dial plate c is caused by moving the locking plate e radially inwards so as to clamp the blade between the inner face of the rib e1 and the flat portion c1 of the dial plate. For this purpose the dial plate is provided with an upstanding stud i which protrudes with a limited amount of clearance through an outwardly coned hole 7c, or bush, in the locking plate e and is adapted to receive a sleeve nut Z having a coned end l1 for co-operation with said coned hole or bush. To allow for radial movement of the locking plate a limited amount of clearance is also provided between the boss al on the head and a hole e2 in the adjacent end of said plate, as clearly seen in Figures 3, 4 and 5.

Normally, the dial and locking plates are rigidly xed to the head by tightening the nut h on the centralstud f. When it is required to adjust the longitudinal position of the blade d relatively to the dial plate, the sleeve nut Z is slackened to reduce the pressure between the rib e1 and the near side of the groove d1, when the blade d can be readily adjusted to any desired position, and re-locked by tightening the said sleeve nut l, the coned end of which oo-operates with the coned hole or bush in the plate e to draw the latter radially inwards.

When it is desired to adjust the angle of the blade d the central nut h is slackened whereupon the dial plate together with the said blade can be turned into any desired angular position on the head a. A spring m is preferably provided between the nut h and the boss al for the purpose of holding the dial plate against the head when the nut 11, is slackened.

I claim:

1. In a device of the character described in combination a dial plate; an adjustable blade mounted slidably in tangential direction of said Ysliding said adjustable blade so as to move it in said radial direction, said locking member having an inclined locking face; and an operating member attached to said dial plate movably in downward direction normal to the direction of sliding of said locking member and adapted to engage during such downward movement said inclined locking face of said locking member and to exert pressure upon the same and thus to slide said locking member in radial direction toward the center of said dial plate.

2. In a device of the character and for the purposes described, in combination a dial plate; an adjustable blade mounted slidably in tangential direction of said dial plate along an edge portion of the same; a locking member mounted slidably in radial direction of said dial plate and engaging during such sliding said adjustable blade so as to move it in said radial direction; and an operating member provided with anV inclined locking face and adapted to engage said locking member, said operating member being attached to said dial platemovably in downward direction normal to the direction of sliding of said locking member so as to exert during such downward movement by means of its inclined locking face pressure upon said locking member and thus to slide the same in radial direction toward the center of said dial plate.

3. In a protractor or like measuring instru-V ment, means for locking an adjustable blade to a calibrated dial plate, comprising in combi; nation a circular head, a locking plate slidably mounted in said dial plate having a rib therein which is adapted to engage a groove in said adjustable blade, an elongated hole in said locking plate which is adapted to engage a boss on said circular head which carries a locking means for said calibrated dial plate, an upstanding stud in said calibrated dial plate, a coned hole in said locking plate through which said upstanding stud passes, a sleeve nut having a coned end mounted upon said upstanding stud so that on the coned yend of the sleeved nut being screwed down into the coned hole in the locking plate the rib therein draws the adjustable blade into intimate contact with the calibrated dial plate and locks same thereto in its adjusted position.

VERNON HENRY GREY. 

